Exploring the Gene-Environment Nexus in Anorexia, Bulimia

Exploring the Gene-Environment Nexus in Anorexia, Bulimia

Although eating disorders have been considered to be largely sociocultural in origin, findings from family, twin and molecular genetic studies conducted during the last decade are refuting that perspective, an expert in genetic epidemiology told attendees at the recent 2nd World Congress on Women's Mental Health in Washington, D.C. (Bulik et al., 2004).

"Twenty years ago when I started in this field, and gave my favorite lecture on eating disorders, it was all about the role of the family and social factors in the etiology of eating disorders," said Cynthia M. Bulik, Ph.D., William R. and Jeanne H. Jordan Distinguished Professor of Eating Disorders in the department of psychiatry and director of the eating disorders program at the University of North Carolina, Chapel Hill. "Both anorexia and bulimia were very much viewed as disorders of choice. These young girls were viewed as trying to emulate some cultural ideal and diet themselves down to a certain weight. Now, any patient would have told you had you listened that wasn't what they were doing. They went far beyond any societal ideal in Cosmopolitan or any other magazine."

Bulik explained that when she and colleagues started talking about genes as being involved in these disorders, "people pretty much thought we were out of our minds." However, the investigators are discovering a complex interplay between genes and the environment leading to the development of anorexia nervosa (AN) and bulimia nervosa (BN).

"Anorexia nervosa has the highest mortality rate of any psychiatric disorder, with the most common causes of death being secondary to starvation and suicide," said Bulik, who is immediate past-president of the Academy for Eating Disorders. The mortality rate at five years is 5%, increasing to 20% at 20-year follow-up (American Psychiatric Association Work Group on Eating Disorders, 2000).

Anorexia nervosa is estimated to affect between 0.5% and 1% of U.S. women and girls. Symptoms and identifying characteristics of AN can be found in the Table. Most commonly, the onset is around puberty, although clinicians are seeing more prepupertal-onset cases. There is also a rise in midlife-onset cases.

"Some of these people are women who had eating disorders or anorexia in their teens and had a period of recovery and then developed it again in midlife. We are also seeing interesting cases of new onset in midlife," Bulik said.

Bulimia nervosa affects 1% to 2% of adolescent and young adult U.S. women. Symptoms and characteristics of the disorder can be found in the Table. "It occurs at all body weights, so you can't tell if someone has bulimia nervosa just by looking at them," she said.